Add a glow to a boolean modifier boundary

Question

I'm building an animation where an object starts as wireframe, then transforms to solid. Blender 2.79b, Cycles.

I have two duplicates of the object, one of which has a wireframe modifier applied. Then I use an object (a cylinder for now) as a boolean object, set to Difference on the wireframe copy and Intersect on the solid copy. The boolean object has its Camera setting turned off in Cycles Settings. By animating the shape, position and scale of the boolean object, I can achieve what I'm looking for.

However, it would be cool to add a glow effect at the boundary, as if there's electric, transformative energy, say. I can't think of a way to do this. Any ideas?

Thanks!

Answer 1

More than one way.

Use a vertex weight proximity modifier after the boolean to assign vertices to a "glow" group, then use a UV warp modifier to translate this glow group into add UV that you can read in your shader.

Our boolean will create new vertices, and vertex weight proximity only affects vertices already assigned to the group, so we'll first need to use a vertex weight edit modifier, immediately following the boolean, to assign all verts to our glow group.

Then our vertex weight proximity modifier overrides that, assigning only vertices that are close to the cylinder (from 0 to 0.13 distance in this case.) We use that vertex group to warp a UV map where all verts have been mapped to 0,0 in order to convert weights to something readable by our nodes. The empties off to the side just establish a 1 unit X difference for the UV warp mod. See Weight paint in cycles nodes?.

I'm not sure how the boolean modifier generates UV coords. I believe it interpolates them from existing coords. Here, any verts created by the boolean are being written properly to our glow map at 0,0.

In our material, we're simply using our UV output from our glow map-- which, remember, represents the proximity of any face of the cylinder-- as strength. I'm doing a little math just to make it look better.